Rascism, hate, and militancy sites have tripled in number over the past year on the Web and within corners of social-networking sites like Facebook, YouTube, Google and Yahoo, according to one vendor tracking them.

Websense is now tracking about 15,000 of these hate and militancy sites, with 1,000 added in just the first five months of this year.

Hate groups include white supremacist Ku Klux Klan-style, Neo-Nazi and skinhead groups, as well as weapon-toting militant extremists of all stripes, including Islamic militants.

Some of the militant and racist sites use "secret symbols or phrases which allow members to identify one another," writes Charles Renart, senior director of advanced content research at Websense Security Labs, in a blog on the subject.  For instance "RAHOWA" is said to be an acronym for "racial holy war" that is used by many white-supremacist groups.

Site owners often try to hide them or make the sites accessible only to their selected "friends," he points out. Numerical symbols such as "88" also frequently indicate a racist or militant site, and "HH" is shorthand for the old Nazi greeting "Heil Hitler." Pagan folklore symbols may--though not necessarily--be used for white-supremacy purposes. Some tend to masquerade as news sites.

Renart says it's hard to say exactly why there appears to be such a strong increase in hate sites in the past year except that Web 2.0-style social networking is something that can be conveniently exploited in "pockets of activity."

The scope of it is international. Most of the activity is in English, though terror videos are usually in Arabic, Renart says.